Pouch type secondary battery and method of manufacturing the same

ABSTRACT

A pouch type secondary battery and a method of manufacturing the same are disclosed. The pouch type secondary battery includes a pouch type case formed by attaching an upper sheet and a lower sheet, and an electrode assembly received in the pouch type case. A polymer coating layer for improving sealability is further included at an outer side portion of the pouch type case, in which the upper sheet and the lower sheet are attached.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of copending U.S. application Ser. No.14/477,523 filed on Sep. 4, 2014, which is a Continuation of PCTInternational Application No. PCT/KR2014/004493 filed on May 20, 2014,which claims priority under 35 U.S.C. § 119(a) to Patent Application No.10-2013-0057390 filed in the Republic of Korea on May 21, 2013, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a pouch type secondary battery and amethod of manufacturing the same.

Description of the Related Art

As the technical development and the demand on mobile devices increase,the demand on secondary batteries as energy sources rapidly increases.Thus, researches on batteries meeting diverse demands have beenconducted substantially. Particularly, rechargeable secondary batteriesreceive attention as power sources of electric vehicles, hybrid electricvehicles, etc.

Secondary batteries may be manufactured in a variety of forms.Typically, demands on a prismatic type secondary battery and a pouchtype secondary battery, having a thin thickness and applicable inproducts such as a cellular phone are high. When considering materials,demands on a lithium secondary battery such as a lithium cobalt polymerbattery having good energy density, discharge voltage and safety arehigh.

Among the above-described batteries, the pouch type secondary battery isfavorable for realizing the slimness and lightweight of portableelectronic devices.

The pouch type secondary battery is manufactured by receiving anelectrode assembly including a cathode, an anode and a separator in apouch type case of an exterior material, performing a first formation ofa battery, degassing using an extra part, cutting and removing the extrapart, and performing a second formation of the battery.

In this case, the safety of the battery may be deteriorated due to thecurrent flowing through an exposed metal layer of the pouch type case bythe cutting, and water permeation and electrolyte loss may be generatedby the loss of packaging capability due to corrosion. Particularly, sidereactions in the battery due to water may be generated, and batteryperformance and safety may be deteriorated.

Therefore, a method of manufacturing a pouch type secondary battery thatmay improve the above-described defects is greatly required.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a pouch type secondarybattery including a polymer coating layer on the outer side portion of apouch type case to improve sealability.

Another aspect of the present invention provides a method ofmanufacturing the pouch type secondary battery.

According to an aspect of the present invention, there is provided apouch type secondary battery including a polymer coating layer on theouter side portion of a pouch type case to improve sealability.

Particularly, according to an aspect of the present invention, there isprovided a pouch type secondary battery including a pouch type caseformed by attaching an upper sheet and a lower sheet, and an electrodeassembly received in the pouch type case, wherein a polymer coatinglayer for improving sealability is further included at an outer sideportion of the pouch type case, in which the upper sheet and the lowersheet are attached.

The polymer may be a UV curable polymer or a thermosetting polymer.

According to another aspect of the present invention, there is provideda method of manufacturing a pouch type secondary battery includingpreparing a pouch type case provided with a receiving part for receivingan electrode assembly and a gas collecting part connected to thereceiving part for collecting gas generated in the receiving part,receiving the electrode assembly in the pouch type case, sealing anouter part of the pouch type case by heat welding, injecting anelectrolyte in the pouch type case, activating a secondary battery andcollecting gas generated during activating through the gas collectingpart, heat welding a boundary of the receiving part and the gascollecting part, cutting and removing the gas collecting part, andforming a polymer coating layer on an outer side portion of the pouchtype case receiving the electrode assembly.

In this case, the polymer coating layer may be formed by a contact typecoating method.

According to the present invention, a polymer coating layer forimproving sealability is formed on the outer side portion of a pouchtype case, and a pouch type secondary battery increasing the reliabilityon the prevention of water permeation and electrolyte leakage may bemanufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1A and 1B are schematic diagrams illustrating pouch type secondarybatteries including a polymer coating layer according to an embodimentof the present invention;

FIG. 2 is a schematic diagram showing a contact type coating method in amethod of manufacturing a pouch type secondary battery according to anembodiment of the present invention; and

FIGS. 3A and 3B are schematic diagrams particularly showing the shape ofa coating head in a method of manufacturing pouch type secondarybatteries according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the inventive concept will be described belowin more detail with reference to the accompanying drawings. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The subject matters described in the embodiments and drawings in thisspecification are just preferred embodiments and are to be consideredillustrative and not restrictive. Accordingly, all such equivalents andmodifications are intended to be included within the scope of thepresent inventive concept.

First, a pouch type secondary battery including a pouch type case formedby attaching an upper sheet and a lower sheet; and an electrode assemblyreceived in the pouch type case, wherein a polymer coating layer forimproving sealability is additionally included on the outer side portionof the pouch type case, in which the upper sheet and the lower sheet areattached, is provided in the present invention.

Particularly, FIGS. 1A and 1B are schematic diagrams illustrating pouchtype secondary batteries including a polymer coating layer according toan embodiment of the present invention.

Referring to FIGS. 1A and 1B, the pouch type secondary battery includesan upper sheet and a lower sheet, and each of the upper sheet and thelower sheet includes an inner layer 101/an adhesive layer 102/a metallayer 103/a corrosion preventing layer 104/an outer layer 105, and theupper sheet and the lower sheet are welded by heat to each other.

The inner layer 101 has heat adhesive properties and plays the role of asealing material, and may include at least one selected from the groupconsisting of a non-oriented polypropylene, a ternary copolymer ofpolypropylene-butylene-ethylene, polypropylene chloride, polyethylene, acopolymer of ethylenepropylene, a copolymer of polyethylene and acrylicacid, and a copolymer of polypropylene and acrylic acid.

The adhesive layer 102 is formed by coating an adhesive resin attachableto the metal layer 103 for the favorable attachment to the metal layer103. The adhesive layer 102 is formed by using a similar material as theinner layer 101, and may include at least one selected from the groupconsisting of polyethylene terephthalate, acid modified polypropyleneand acid modified polyethylene to improve the adhesiveness with themetal layer 103.

The metal layer 103 is provided to keep mechanical strength and plays arole as a barrier layer of humidity and oxygen. The metal layer 103 mayinclude one or a mixture selected from the group consisting of iron(Fe), carbon (C), chromium (Cr), manganese (Mn), nickel (Ni) andaluminum (Al). More particularly, the metal layer 103 may include atleast one selected from the group consisting of aluminum; an alloy ofiron, carbon, chromium and manganese; and an alloy of iron, carbon,chromium and nickel.

The outer layer 105 acts as a base and a passivation layer and mayinclude at least one selected from the group consisting of polyethylene,polyphenylene ether, polyimide, polypropylene, casted polypropylene,polyether terephthalate and polyphenylene sulfide. The corrosionpreventing layer 104 may be additionally disposed between the outerlayer 105 and the metal layer 103.

The corrosion preventing layer 104 is a layer having resistance tocorrosion generated by an electrolyte and may include zirconium,chromium or a mixture thereof.

In addition, the electrode assembly is an electricity generating elementin which a cathode and an anode are stacked in order with a separatordisposed therebetween and has a stacked type or a stack and folding typestructure. Electrode tabs are extended from each of electrode plates ofthe electrode assembly, and electrode terminals are electricallyconnected to each of a plurality of the electrode tabs extended fromeach of the electrode plates by, for example, welding. And a portion ofthe electrode terminals is exposed to exterior of the pouch typesecondary battery for the electrical connection of a battery body withexterior.

Meanwhile, in the pouch type secondary battery, a first formation of abattery is performed, and a degassing process for removing gas generatedduring initial charging and discharging is performed. Then, a gascollecting part is cut and removed, and a second formation of thebattery is performed. In this case, a metal layer configured to form apouch type case is exposed by the cutting process and corroded to losepackaging capability. Thus, water permeation and electrolyte loss may begenerated, thereby deteriorating the performance and safety of thebattery.

To solve the above-described defects, in the present invention, apolymer coating layer 106 is additionally formed on the outer sideportion of the pouch type case, in which the upper sheet and the lowersheet are attached, to improve sealability before or after performingthe second formation process. Thus, the current flow of the metal layerforming the pouch type case with other metal materials may be prevented,and the outer side of the pouch type case may be passivated in afollowing process. Therefore, adverse influence in the subsequentprocess may be prevented.

The position of the polymer coating layer formed is not specificallylimited. The polymer coating layer may be formed only on the outer sideportion perpendicular to an extruded surface of the electrode terminalsof an electrode assembly as shown in FIG. 1B, or may be selectivelyformed on the outer side portion horizontal to the extruded surface ofthe electrode terminals. Most preferably, the polymer coating layer maybe formed on the entire outer side portion of the pouch type case asshown in FIG. 1A. In this case, the electrode terminals may include acathode terminal and an anode terminal, and may be disposed on the sameside of the electrode assembly and may be disposed on each of both sidesfacing to each other, respectively. For example, the electrode terminalsmay be disposed on one side of a battery cell, on both sides facing toeach other so that the electrode terminals may not make electricalcontact with each other.

In addition, in the pouch type secondary battery of the presentinvention, a polymer may include all kinds of polymer providinginsulating properties after being coated and cured. The polymer may be aUV curable polymer or a thermosetting polymer, and is not limitedthereto.

Particularly, the UV curable polymer may include a single material or amixture selected from an organic isocyanate compound having two or moreisocyanate groups and a hydroxyalkyl (meth)acrylate resin modified witha polylactone-based compound.

In addition, the thermosetting polymer may include a single material ora mixture of two or more selected from the group consisting ofepoxyalkyl (meth) acrylate, allyl glycidyl ether, allyl glycidyl ester,aryl glycidyl ether, aryl glycidyl ester, glycidyl5-norbornene-2-methyl-2-carboxylate (a mixture of endo- andexo-compounds), 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene, glycidyl(meth)acrylate, glycidyl α-ethyl (meth)acrylate, glycidyl α-n-propyl(meth)acrylate, glycidyl α-n-butyl (meth) acrylate, methylglycidyl(meth) acrylate, 3,4-epoxybutyl (meth) acrylate, 4,5-epoxypentyl (meth)acrylate, 5,6-epoxyheptyl (meth) acrylate, and 6,7-epoxyheptylα-ethylacrylate.

In addition, the thickness of the polymer coating layer 106 is notspecifically limited and is formed to the smallest thickness only ifrestricting the permeation of water depending on the kind of the polymerforming the coating layer. The polymer coating layer 106 may be formedas thick as possible within the range of keeping the exterior standardof the pouch type secondary battery.

In addition, there is provided a method of manufacturing a pouch typesecondary battery including preparing a pouch type case provided with areceiving part for receiving an electrode assembly and a gas collectingpart connected to the receiving part for collecting gas generated in thereceiving part; receiving the electrode assembly in the pouch type case;sealing an outer part of the pouch type case by heat welding; injectingan electrolyte in the pouch type case; activating a secondary batteryand collecting gas generated during activating through the gascollecting part; heat welding a boundary of the receiving part and thegas collecting part; cutting and removing the gas collecting part; andforming a polymer coating layer on an outer side portion of the pouchtype case receiving the electrode assembly, in the present invention.

In the method of the present invention, the forming of the polymercoating layer may be performed before or after a second batteryformation process, and may preferably be performed after the secondbattery formation process.

In addition, the polymer coating layer may be formed by a contact typecoating method.

The contact type coating method may be performed by using a spongecoating head or a roller coating head. Particularly, since the polymercoating layer of the present invention is coated after dissolving thepolymer in water or in an organic solvent, the coating method is notspecifically limited, and an appropriate method may be used.

In addition, after forming the polymer coating layer, a common heatdrying process may be additionally performed for drying the coatinglayer.

FIG. 2 is a schematic diagram showing a contact type coating method in amethod of manufacturing a pouch type secondary battery according to anembodiment of the present invention.

Referring to FIG. 2, after performing the degassing process, the gascollecting part is removed, and the second battery formation isperformed. Then, a polymer coating layer 203 is formed on the entiresurface of an exposed pouch type case.

In this case, the position of the polymer coating layer is notspecifically limited, and the polymer coating layer may be formed onlyon the outer side portion perpendicular to extruded sides of electrodeterminals 201 and 202, or may be selectively formed on the outer sideportion horizontal to the extruded sides of the electrode terminals ofan electrode assembly. However, the polymer coating layer may preferablybe formed on the entire outer side portion of the pouch type case.

The polymer coating layer may be formed by using a contact type coatingmethod.

That is, after contacting a coating apparatus provided with a coatinghead 204 and a vessel 205 containing a polymer material to the outerside portion of the pouch type case, coating may be performed along theouter side portion.

The coating head 204 of a contact type may be a sponge coating head 204a as shown in FIG. 3A or a roller coating head 204 b of a fiber-basedmaterial as shown in FIG. 3B.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

EXPLANATION ON DESIGNATED SYMBOLS

-   -   100: upper sheet or lower sheet of the pouch type secondary        battery    -   101: inner layer    -   102: adhesive layer    -   103: metal layer    -   104: corrosion preventing layer    -   105: outer layer    -   106, 203: polymer coating layer    -   201, 202: electrode terminal of the pouch type secondary battery    -   204: coating head    -   204 a: sponge coating head    -   204 b: roller coating head    -   205: vessel of coating material

What is claimed is:
 1. A method of manufacturing a pouch type secondarybattery, comprising: preparing a pouch type case provided with areceiving part for receiving an electrode assembly and a gas collectingpart connected to the receiving part for collecting gas generated in thereceiving part; receiving the electrode assembly in the pouch type case;sealing an outer part of the pouch type case by heat welding; injectingan electrolyte in the pouch type case; activating the pouch typesecondary battery and collecting gas generated during activating throughthe gas collecting part; heat welding a boundary of the receiving partand the gas collecting part; cutting and removing the gas collectingpart; and forming a polymer coating layer on an outer side portion ofthe pouch type case receiving the electrode assembly, wherein theforming of the polymer coating layer is performed by a contact typecoating method.
 2. The method of manufacturing a pouch type secondarybattery of claim 1, wherein the contact type coating method is performedby using a sponge coating head or a roller coating head.
 3. The methodof manufacturing a pouch type secondary battery of claim 1, wherein thepouch type case is formed by attaching an upper sheet and a lower sheet.4. The method of manufacturing a pouch type secondary battery of claim3, wherein each of the upper sheet and the lower sheet includes an innerlayer, a metal layer, and an outer layer.
 5. The method of manufacturinga pouch type secondary battery of claim 1, wherein the polymer is a UVcurable polymer or a thermosetting polymer.
 6. The method ofmanufacturing a pouch type secondary battery of claim 5, wherein the UVcurable polymer includes at least one selected from the group consistingof an organic isocyanate compound having two or more isocyanate groupsand a hydroxyalkyl (meth)acrylate resin modified with apolylactone-based compound.
 7. The method of manufacturing a pouch typesecondary battery of claim 5, wherein the thermosetting polymer includesat least one selected from the group consisting of epoxyalkyl(meth)acrylate, allyl glycidyl ether, allyl glycidyl ester, arylglycidyl ether, aryl glycidyl ester, glycidyl5-norbornene-2-methyl-2-carboxylate (a mixture of endo- andexo-compounds), 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene, glycidyl(meth)acrylate, glycidyl α-ethyl (meth)acrylate, glycidyl α-n-propyl(meth)acrylate, glycidyl α-n-butyl (meth) acrylate, methylglycidyl(meth) acrylate, 3,4-epoxybutyl (meth) acrylate, 4,5-epoxypentyl (meth)acrylate, 5,6-epoxyheptyl (meth) acrylate, and 6,7-epoxyheptylα-ethylacrylate.
 8. The method of manufacturing a pouch type secondarybattery of claim 1, wherein the outer side portion is perpendicular toan extruded surface of an electrode terminal of the electrode assembly.9. The method of manufacturing a pouch type secondary battery of claim1, wherein the outer side portion is horizontal to an extruded surfaceof an electrode terminal of the electrode assembly.
 10. The method ofmanufacturing a pouch type secondary battery of claim 1, wherein thepolymer coating layer is formed on an entire surface of the outer sideportion of the pouch type case, which is an entire surface of the pouchtype case.